HI. I am caching the valid recipients on the MX server, and then it has enough knowledge for queueing: [Mimedefang] My semi-cached version of md_check_against_smtp_server: http://lists.roaringpenguin.com/pipermail/mimedefang/2006-December/031463.html Yizhar Hurwitz, http://yizhar.mvps.org